Response of Cortical and Cancellous Bones to Mild Calcium Deficiency in Young Growing Female Rats: A Bone Histomorphometry Study

Calcium affects sternal mass by effects on osteoclast differentiation and function in meat ducks fed low nutrient density diets

Genetic progress and increasing nutrient density for greater body mass and meat yield in poultry has inadvertently led to an imbalance between pectorales mass and sternal development which may or may not be detrimental to productivity and welfare. Slowing weight gain while promoting bone mineralization could positively influence sternal health. Thus, the present study aimed to evaluate the effect of graded calcium (Ca) supplementation in low nutrient density (LND) diets on sternal mass and bone turnover in meat ducks. Male meat ducks (720, 15-day-old) were randomly assigned and fed a standard nutrient density positive control (PC) diet, and 4 LND diets with 0.5, 0.7, 0.9, and 1.1% Ca, respectively. Metabolic energy (ME) was reduced in the LND by 9.5 and 16.3% at 15-35 D and 36-56 D compared to PC diet, respectively, while maintaining proportionate essential nutrient proportions to energy similar as in the PC diet. Although the 0.9% Ca LND diet decreased body weight and sternal dimension, it increased the relative sternum weight, the trabecular bone volume/tissue volume (BV/TV) and Ca content of the sternum compared with PC diet. Feeding 0.7% or more Ca with the LND diet significantly increased the mineral content, bone density, BV/TV, and trabecular number of the sternum for 49-days-old ducks. Furthermore, the LND diet with 0.7% or more Ca-increased osteocyte-specific gene mRNA and osteoprotegerin (OPG) expression, and it blocked the expression of cathepsin K and decreased osteoclasts number per bone surface. Tartrate-resistant acid phosphatase (TRAP) staining also revealed that the addition 0.7% or more Ca to the LND diet significantly decreased the number of osteoclasts compared with the 0.5% Ca LND diet. Meanwhile TRAP activity in serum was significantly decreased in 0.7% or more Ca-treated groups. We concluded that LND diet with 0.7% or more Ca may maintain optimal sternal mass through suppressing bone resorption for meat duck.

Effect of graded calcium supplementation in low-nutrient density feed on tibia composition and bone turnover in meat ducks

Both genetic selection and increasing nutrient density for improving growth performance had inadvertently increased leg problems of meat ducks, which adversely affects animal welfare. We hypothesised that slowing weight gain with improving tibia quality probably enhanced tibial mechanical properties and alleviated leg deformities. Therefore, the present study aimed to evaluate the effect of graded Ca supplementation in a low-nutrient density (LND) diet on tibia composition and bone turnover in meat ducks. A total of 720 15-d-old male meat ducks were randomly assigned and fed a standard nutrient density positive control (PC) diet containing 0·9 % Ca, and four LND diets with 0·5, 0·7, 0·9 and 1·1 % Ca, respectively. Ducks fed the 0·5 % Ca LND diet and the PC diet had higher incidence of tibial dyschondroplasia (TD). When compared with the 0·5 % Ca LND diet, LND diets with ≥0·7 % Ca significantly improved tibia composition, microarchitecture and mechanical properties, and consequently decreased the incidence of TD. Furthermore, LND diets with ≥0·7 % Ca increased osteocyte-specific gene mRNA expression, blocked the expression of osteoblast differentiation marker genes including osteocalcin, collagenase-1 and alkaline phosphatase (ALP), and also decreased the expression of osteoclast differentiation genes, such as vacuolar-type H+-ATPase, cathepsin K and receptor activator of NF-κB. Meanwhile bone markers such as serum ALP, osteocalcin (both osteoblast markers) and tartrate-resistant acid phosphatase (an osteoclast marker) were significantly decreased in at least 0·7 % Ca treated groups. These findings indicated that LND diets with ≥0·7 % Ca decreased bone turnover, which subsequently increased tibia quality for 35-d-old meat ducks.

Kit W-sh Mutation Prevents Cancellous Bone Loss during Calcium Deprivation

Calcium is essential for normal bone growth and development. Inadequate calcium intake increases the risk of osteoporosis and fractures. Kit ligand/c-Kit signaling plays an important role in regulating bone homeostasis. Mice with c-Kit mutations are osteopenic. The present study aimed to investigate whether impairment of or reduction in c-Kit signaling affects bone turnover during calcium deprivation. Three-week-old male WBB6F1/J-Kit ^W /Kit ^W-v /J (W/W ^v ) mice with c-Kit point mutation, Kit ^W-sh /HNihrJaeBsmJ (W ^sh /W ^sh ) mice with an inversion mutation in the regulatory elements upstream of the c-Kit promoter region, and their wild-type controls (WT) were fed either a normal (0.6% calcium) or a low calcium diet (0.02% calcium) for 3 weeks. μCT analysis indicated that both mutants fed normal calcium diet had significantly decreased cortical thickness and cancellous bone volume compared to WT. The low calcium diet resulted in a comparable reduction in cortical bone volume and cortical thickness in the W/W ^v and W ^sh /W ^sh mice, and their corresponding controls. As expected, the low calcium diet induced cancellous bone loss in the W/W ^v mice. In contrast, W ^sh /W ^sh cancellous bone did not respond to this diet. This c-Kit mutation prevented cancellous bone loss by antagonizing the low calcium diet-induced increase in osteoblast and osteoclast numbers in the W ^sh /W ^sh mice. Gene expression profiling showed that calcium deficiency increased Osx, Ocn, Alp, type I collagen, c-Fms, M-CSF, and RANKL/OPG mRNA expression in controls; however, the W ^sh mutation suppressed these effects. Our findings indicate that although calcium restriction increased bone turnover, leading to osteopenia, the decreased c-Kit expression levels in the W ^sh /W ^sh mice prevented the low calcium diet-induced increase in cancellous bone turnover and bone loss but not the cortical bone loss.

Altered bone microarchitecture and gene expression profile due to calcium deficiency in a mouse model of myeloma

It is not clear why patients with an indolent form of multiple myeloma (MM) develop into an aggressive form with poor prognostic. We investigated the effect of a dietary calcium deficiency on tumor growth, osteolysis and gene expression in the 5T2MM murine model. Two groups of C57BL/KaLwRij mice received 5T2MM cells and started a diet with normal (0.8%; "normal-Ca-MM") or low calcium content (0.05%; "low-Ca-MM"). Two control groups (without 5T2MM cells) received either a normal or low calcium diet (normal-Ca and low-Ca groups). Tumor growth, osteolysis and marrow gene expression of the Wnt pathway, RANKL and MIP-1α were monitored at 6, 8 and 10 weeks (w) after cell injection. In low-Ca mice, serum level of PTH was higher after 10w; microCT showed trabecular bone loss and decrease of cortical thickness at the tibia. A higher M-protein level was evidenced at 10w and 4 mice developed paraplegia at 8/9w in low-Ca-MM group only. Numerous cortical perforations of the tibia were observed in MM groups with a marked decrease in cortical thickness in low-Ca-MM. At 6w, osteoclast number from the endosteum was significantly higher in low-Ca-MM compared to normal-Ca MM. This observation was not found at 8 and 10w. MicroCT of the lumbar vertebrae showed dramatic bone destruction in the low-Ca-MM group. qPCR revealed no difference in RANKL expression whereas differences were obtained in the expression of Lrp5/Lrp6 and MIP-1α from 6w. A low calcium diet induced higher bone destruction in the tibia and vertebra associated with an earlier decrease in bone formation level and a higher increase in bone resorption level at early time in the MM development.

Dissolution of the inorganic phase of bone leading to release of calcium regulates osteoclast survival

Osteoclasts are the sole cells possessing the ability to resorb calcified bone matrix. This occurs via secretion of hydrochloric acid mediated by the V-ATPase and the chloride channel ClC-7. Loss of acidification leads to osteopetrosis characterized by ablation of bone resorption and increased osteoclast numbers, indicating increased life span of the osteoclasts. To investigate the role of the inorganic phase of bone with respect to osteoclast life span, we used the V-ATPase inhibitor bafilomycin and the calcium uptake antagonist ryanodine on human osteoclasts cultured on calcified and decalcified bone slices. Bafilomycin inhibited bone resorption and increased osteoclast survival on calcified but not decalcified bones. Ryanodine attenuated calcium uptake and thereby augmented osteoclast survival on calcified bones. In summary, we found that acidification leading to calcium release from bone during resorption controls osteoclast survival, potentially explaining the increased numbers of osteoclasts in patients with osteopetrosis.

Calcium deficiency-induced secondary hyperparathyroidism and osteopenia are rapidly reversible with calcium supplementation in growing rabbit pups

The reversibility of osteopenia secondary to isolated Ca deficiency (CaDef) is still not clear. We studied the effect of severe CaDef on Ca homeostasis and bone accrual in a ‘hypercalcaemic’ animal, the rabbit, during the post-weaning period and its reversibility on Ca supplementation. Male Belgian 5-week-old rabbit pups were fed CaDef diet (0·026% Ca) for 10 weeks. As compared with those fed with a normal chow diet (0·45% Ca), CaDef pups developed significant hypocalcaemia (P<0·05), hypocalciuria (urinary Ca 76 (sem 12) V 17 (sem 1) mg/l;P<0·005), hypophosphataemia (serum inorganic P 100 (sem 6) V. 65 (sem 4) mg/l; P<0·005), secondary hyperparathyroidism (SHPT) (serum intact parathyroid hormone human equivalent 18·2 (sem 1·4) V. 125·0 (sem 4·5) pg/ml; P<0·001) and elevated serum calcitriol levels (34·0 (sem 3·9) V. 91·0 (sem 1·0) pg/ml; v<0·005). Elevated urinary C-terminal telopeptide of class I collagen (P<0·005) and total serum alkaline phosphatase (P<0·005) suggested increased bone turnover. There was a significantly lower gain in bone mineral density (BMD) and bone mineral content (BMC) in the whole body and lumbar spine in vivo, and various sub-regions of the femur and tibia in vitro.Supplementation of adequate Ca (0·45% Ca) after 15 weeks on the normal diet resulted in rapid catch-up growth, and resolution of SHPT. Rapid gain in various BMD and BMC parameters continued at 30 weeks of age, and both were comparable with those in rabbits on a normal diet. We conclude that Ca deficiency-induced SHPT and poor bone accrual in growing rabbit pups are rapidly reversible with Ca supplementation. The present study indicates that early intervention may be a more appropriate window period for human nutritional corrective measures.

Iron restriction negatively affects bone in female rats and mineralization of hFOB osteoblast cells

We previously reported that severe iron deficiency negatively affects bone microarchitecture. Here we determined whether marginal iron restriction that reflects some human consumption patterns could have similar consequences. Thirty-two weanling female rats were randomly divided into four groups and fed the following diets for 10 weeks: (i) iron-adequate, calcium-adequate (FeA:CaA), (ii) calcium-restricted (FeA:CaR), (iii) iron-restricted (FeR:CaA), and (iv) both calcium- and iron-restricted (FeR:CaR) diets. DEXA analysis revealed that CaR decreased bone mineral density (BMD), and FeR decreased whole-body bone mineral content (BMC). Iron-restricted and calcium-restricted groups had lower BMD than did their adequate counterparts. All treatment-restricted groups had lower BMD in the fourth lumbar (L-4) vertebrae than the FeA:CaA group. Vertebrae BMD was lower in all treatment groups compared to the control group, and for BMC, the CaR groups were lower than the CaA groups and the FeR groups were lower that the FeA groups, and BMC were lower in iron- and calcium-restricted groups. The microarchitecture of the L-4 vertebrae was compromised in FeA:CaR, FeR:CaA, and FeR:CaR: (i) the connectivity density was reduced by FeR and by CaR; and (ii) trabecular number was decreased and trabecular separation was increased by FeR. Cortical thickness of the femur was reduced by both FeR and CaR. Finite element analysis revealed that L-4 vertebrae from the FeR:CaA group had greater internal stress with an applied force than the FeA:CaA group and, thus, would be more likely to break. Chelation of iron in cultured osteoblast cells impaired mineralization but had no impact upon Type I collagen deposition. Iron depletion, similar to that occurring among some human populations, reduced bone strength and microarchitecture based on the in vivo and in vitro results reported here. Impaired mineralization with iron depletion appears to be a possible mechanism for the observed bone abnormalities.